1. Field of the Invention
The present invention generally relates to apparatus for recording or/and reproducing information and methods for saving power thereof, and more particularly to apparatus for recording or/and reproducing information to/from a medium and a method for saving power thereof.
Recently, saving power in electronic devices has become more important. Also, saving power in information recording/reproducing apparatus such as a magnetic disk apparatus has been desired. Especially, in the information recording/reproducing apparatus such as a magnetic disk apparatus, the rotation speed of the medium and a driving clock for an internal LSI (Large scale Integration) have increased every year, and access time has shortened. In addition, regardless of increasing the rotation speed of the medium, an activate or start-up time until a regular rotation is reached has also been shortened. However, current use has increased and power consumption has increased while making the activation time shorter.
2. Description of the Related Art
FIG. 1 is a perspective view of a magnetic disk apparatus. FIG. 2 is a block diagram of the magnetic disk apparatus. The magnetic disk apparatus 1 includes an enclosure 11 and a printed circuit substrate 12. The enclosure 11 includes a magnetic disk 21, a spindle motor (SPM) 22, a magnetic head 23, a head arm 24, a voice coil motor (VCM) 25, and a head IC 26, which are mounted inside a case 27 and a case cover 28.
The magnetic head 23 is fixed to a tip of head arm 24 and arranged facing towards the magnetic disk 21. A recording current corresponding to data or other information is supplied from the head IC 26 to the magnetic head 23 when information is recorded. Magnetic flux is generated by the recording current at the magnetic head 23. The magnetic flux generated by the magnetic head 23 affects the magnetic disk 21 and magnetizes the magnetic disk 21. As described above, the information is magnetically recorded to the magnetic disk 21.
Also, when the information is reproduced, the magnetic pattern of the magnetic disk 21 affects the magnetic head 23 and a reproducing signal occurs in the magnetic head 23. The reproducing current is supplied to the head IC 26. The head IC 26 amplifies the reproducing current from the magnetic head 23 and supplies it to the printed circuit substrate 12.
The print circuit substrate 12 includes an HDC (Hard Disk Drive Controller) 31, a buffer memory 32, an RDC (Read Channel) 33, an SVD (Servo Demodulator) 34, a DSP (Digital Signal Processor) 35, an SVC (Servo Combo) 36, an MCU (Micro-Control Unit) 37, a memory 38, and an oscillator 39. The RDC 33 modulates record information, generates a record signal, and supplies the head IC 26, and demodulates information from the reproducing signal from the head IC 26 and supplies it to the HDC 31. The HDC 31 controls the buffer memory 32, a SCSI (Small Computer System Interface) protocol control, and an ECC (Error Correction Code) control as well as controlling reproducing and recording operations by a formatter function.
The reproducing signal is supplied from the RDC 33 to the SVD 34. The SVD 34 demodulates servo information from the reproducing signal from the RDC 33. The servo information demodulated by the SVD 34 is supplied to the MCU 37 and the DSP 35. The MCU 37 and the DSP 35 independently operate by firmware recorded in the memory 38, and control the RDC 33, the SVD 34, the SVC 36, and HDC 31.
FIG. 3 is a diagram showing a supply path of the internal clock of the magnetic disk apparatus. In FIG. 3, parts that are the same as the ones in FIG. 2 are indicated by the same reference numerals and the explanation thereof will be omitted.
The oscillator 39 oscillates at an oscillation frequency of 20 MHz. An output oscillating signal of the oscillator 39 is supplied to the SVD 34, the DSP 35, and the MCU 37. The SVD 34 and DSP 35 divide an oscillating signal of a frequency 20 MHz from the oscillator 39 by using a PLL circuit or the like, generate an operating clock, and conduct a process based on the operation clock.
In addition, the MCU 37 divides the oscillating signal of the frequency 20 MHz from the oscillator 39 by using the PLL circuit or the like, generates an operation clock, and conducts a process based on the operation clock. The MCU 37 multiplies the oscillating signal of the frequency 20 MHz from the oscillator 39 by using the PLL circuit or the like, generates a clock of a frequency 40 MHz by dividing the oscillating signal, and supplies the clock to the HDC 31 and RDC 33. The HDC 31 and the RDC 33 generate an operation clock from the clock of the frequency 40 MHz, and conduct a process based on the operation clock.
At this time, for example, the MCU 37 can conduct a power save based on the firmware. Conventionally, as a power save of the magnetic disk apparatus 1, generally, the following first, second, and third power save approaches are used.
As for the first power save approach, if a command is not issued from an upper apparatus within a predetermined time, the HDC 31, the SVD 34, and the DSP 35 normally operate only when the MCU 37 reads. Otherwise, the HDC 11, the SVD 34, and the DSP 35 are placed in a partial power save status. In the first power save mode, power consumption can be reduced for the magnetic disk apparatus 1 in a tracking operation in which a recording/reproducing operation is not conducted to the magnetic disk 21. However, power save for the head IC 26 is not conducted.
In the second power save approach, the operation clocks of the HDC 31, the RDC 33, the SVD 34, the DSP 35, and MCU 37 are slowed. Power consumption can be reduced because the HDC 31, the RDC 33, the SVD 34, the DSP 35, and MCU 37 normally operate at high speed.
Furthermore, the third power save approach sets a switch ON by a transistor or the like between each of various LSIs such as the HDC 31, the RDC 33, the SVD 34, the DSP 35, and the MCU 37, and each power source thereof, when the magnetic disk apparatus 1 is activated. In the third power save approach, the power consumption can be reduced by stopping unnecessary operations of the LSIs when the magnetic disk apparatus 1 is activated but has not reached steady state.
In a recent magnetic disk apparatus, power consumption has increased because the rotation speed and the operation clock frequency are increased. Accordingly, actual power consumption has increased more than the power consumption has been reduced by the first power save, the second power save, and the third power save approaches described above. Therefore, it is desired to further improve the power save approaches.